If Bey dies (which I hope doesn't happen for a long time), I'd expect material to come out for YEARS and YEARS.
She recorded 40+ songs for DIL (some of which ended up on Speak My Mind) 30+ songs for B'Day, 30+ songs for IASF, 45+ songs for 4 & God knows how many for 5.
And then if you factor in Destiny's Child demos....
She can literally put out 20 albums with just unused tracks.